Labor Party factional leaders are searching for a face-saving compromise on the issue of same-sex marriage ahead of the ALP national conference, which starts today.

On Wednesday night, Queensland's Parliament upped the pressure on federal Labor when it joined Victoria, Tasmania and the ACT in passing legislation recognising same-sex civil partnerships.

Opinion polls show that the majority of Australians back same-sex civil unions but Prime Minister Julia Gillard is flatly opposed to gay marriage.

Ms Gillard is suggesting the issue be put to a conscience vote in Parliament - a vote which would be lost because the Coalition would vote against any change.

But the internal push to change the ALP platform is led by Finance Minister Penny Wong from the Left faction, and ACT Deputy Chief Minister Andrew Barr from the Right.

"I'm proposing to insert a new set of words into Labor's platform which would commit the Labor Party into amending the Marriage Act to ensure equal access to marriage for all couples, irrespective of sex, who have a mutual commitment to a shared life," Mr Barr told Radio National.

"This is a political push. I think it's also part of the Green agenda, and I think it will be detrimental to the Labor vote - the traditional vote of the people that we represent, the mums and dads in the community; Australian workers out there won't want to see us make this move."

Senator Polley says if the party decides to endorse same-sex marriage without permitting a conscience vote and the issue is then put to a vote in Federal Parliament, she would consider crossing the floor.

"This would be for me a huge decision that I'd have to make, because I firmly believe that we shouldn't be changing the Marriage Act and the definition of marriage," she said.

"I think it's about whether the Labor Party will put up any resolution.

"I think you'll find that when we return to Parliament next year, Bob Brown and the Greens will introduce something in the House of Reps and the Senate and they are trying to wedge us.

"I would find it very, very difficult to go against my conscience, and I know that there's many other members of Caucus that feel very deeply and we will be trying to get every vote across the line to support the Prime Minister between now and when the vote takes place on Saturday."